Browsing by Author "Castello, Joan"
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- Data packageData from: Geolocators reveal variation and sex-specific differences in the migratory strategies of a long-distance migrant(2021-12-29) Bell, Fraser; Bearhop, Stuart; Briedis, Martins; El Harouchi, Myriam; Bell, Sophie C.; Castello, Joan; Burgess, MalcolmSongbird populations are in decline all over the world, and our understanding of the causal mechanisms remains surprisingly limited. It is important to identify the extent of individual variations in migratory behaviour to better understand species' ability to respond to environmental change. We describe the annual migratory behaviour of British breeding European Pied Flycatchers Ficedula hypoleuca by using light-recording geolocators. During both autumn and spring migrations, individuals used previously unknown staging areas on the Iberian Peninsula and northern West Africa. Furthermore, partial sex-specific segregation in the location of non-breeding areas was observed within West Africa, with females located west of males. We also found sex-based phenological differences, with females staying longer in non-breeding areas and undertaking the spring Sahara Desert crossing later than males. Irrespective of sex, multiple use of the two predominant staging regions was identified during both migrations, with 63% of individuals stopping more than once in these regions. We also identified instances of migratory behaviours rarely documented in individually tracked songbirds. These include making daytime landfall during the Sahara crossing, and a case of a temporary retreat migration, with an individual aborting a spring Sahara crossing before making a second successful crossing 14 days later. Together, our results show variability in migratory behaviour both between sexes and between individuals. For Pied Flycatchers, such flexible migratory behaviour may increase their resilience to environmental change.
- Data packageData from: Loop-migration and non-breeding locations of British breeding Wood Warblers Phylloscopus sibilatrix(2022-11-22) Burgess, Malcolm D.; Castello, Joan; Davis, Tony; Hewson, ChrisCapsule: British breeding Wood Warblers Phylloscopus sibilatrix show a clockwise loop migration incorporating stops in southern Europe, the Sahel, and the humid forest zone of West Africa. Aims: To determine autumn and spring migration routes, the location and duration of stopover sites on migration, and the location of non-breeding areas of British breeding Wood Warblers. Methods: In 2016 and 2018 we deployed geolocators to male Wood Warblers on Dartmoor, Devon, and in the New Forest, Hampshire. We retrieved four geolocators from returning birds in 2017, 2019, and 2020. Results: Male Wood Warblers departed breeding sites in late July and stopped for most of August in central southern Europe, crossed the Sahara by a non-stop night and day flight immediately followed by a short stop, and then migrated west to a longer stopover in the Sahel. Final non-breeding destinations were in an area of West Africa covering Guinea, Sierra Leone, and Liberia. Two were tracked on spring migration, again crossing the Sahara via a non-stop flight before migrating through Western Europe to complete a clockwise loop migration back to Britain. Conclusion: All tracked Wood Warblers used stopovers for at least three weeks in three distinct regions, in central southern Europe, in the Sahel, and in the humid zone of West Africa. Although the limitations of geolocation prevent matching locations with habitat, these regions are broadly characterized by distinct forest or woodland habitat types, which differ from breeding habitat. All four tracks showed similar patterns in route, stopover behaviour, and timings, suggesting they may be representative of males in these breeding populations, and potentially of other British and western European Wood Warbler populations.
- Data packageData from: Weak migratory connectivity, loop migration and multiple non-breeding site use in British breeding Whinchats Saxicola rubetra(2020-06-18) Burgess, Malcolm D.; Finch, Tom; Border, Jennifer A.; Castello, Joan; Conway, Greg; Ketcher, Martin; Lawrence, Mark; Orsman, Christopher J.; Mateos, Judit; Proud, Amanda; Westerburg, Stephen; Wiffen, Tina; Henderson, Ian G.Determining the links between breeding populations and the pressures, threats and conditions they experience presents a challenge for the conservation of migratory birds which can use multiple sites separated by hundreds to thousands of kilometres. Furthermore, migratory connectivity – the connections made by migrating individuals between networks of breeding and non‐breeding sites – has important implications for population dynamics. The Whinchat Saxicola rubetra is declining across its range, and tracking data from a single African non‐breeding site implies high migratory spread. We used geolocators to describe the migration routes and non‐breeding areas of 20 Whinchats from three British breeding populations. As expected, migratory spread was high, with birds from the three populations overlapping across a wide area of West Africa. On average, in non‐breeding areas, British breeding Whinchats were located 652 km apart from one another, with some likely to share non‐breeding areas with individuals from breeding populations as far east as Russia. Four males made a direct non‐breeding season movement to a second, more westerly, non‐breeding location in January. Autumn migration was through Iberia and around the western edge of the Sahara Desert, whereas spring migration was more direct, indicating an anticlockwise loop migration. Weak migratory connectivity implies that Whinchat populations are somewhat buffered against local changes in non‐breeding conditions. If non‐breeding season processes have played a role in the species’ decline, then large‐scale drivers are likely to be the cause, although processes operating on migration, or interactions between breeding and non‐breeding processes, cannot be ruled out.